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</style>
<title>基础</title>

</head>
<body>
<h1>基础</h1>

<ul>
<li><a href="#configuration">配置</a></li>
<li><a href="#running-queries">执行查询</a></li>
<li><a href="#database-transactions">数据库事务</a></li>
<li><a href="#accessing-connections">获取连接</a></li>
<li><a href="#query-logging">查询日志</a></li>
</ul>


<p><a name="configuration"></a></p>

<h2>配置</h2>

<p>Laravel 使得连接数据库和执行查询都非常的简单。数据库配置文件位于 <code>app/config/database.php</code>。在这个文件中您可以定义所有数据库连接，并且指定哪一个连接是被默认使用的。这个文件提供了所有支持的数据库系统的样例。</p>

<p>当前 Laravel 支持四种数据库系统：MySQL, Postgres, SQLite 以及 SQL Server。</p>

<p><a name="running-queries"></a></p>

<h2>执行查询</h2>

<p>一旦您已经配置好数据库连接，您可以使用 <code>DB</code> 类执行查询。</p>

<p><strong>执行一个Select查询</strong></p>

<pre><code>$results = DB::select('select * from users where id = ?', array(1));
</code></pre>

<p><code>select</code> 方法通常返回一个查询结果的数组。</p>

<p><strong>执行一个插入表达式</strong></p>

<pre><code>DB::insert('insert into users (id, name) values (?, ?)', array(1, 'Dayle'));
</code></pre>

<p><strong>执行一个更新表达式</strong></p>

<pre><code>DB::update('update users set votes = 100 where name = ?', array('John'));
</code></pre>

<p><strong>执行一个删除表达式</strong></p>

<pre><code>DB::delete('delete from users');
</code></pre>

<blockquote><p><strong>注意:</strong> <code>update</code> 和 <code>delete</code> 表达式返回该操作影响的行数。</p></blockquote>

<p><strong>执行一个普通的表达式</strong></p>

<pre><code>DB::statement('drop table users');
</code></pre>

<p>您可以使用 <code>DB::listen</code> 函数监听查询事件：</p>

<p><strong>监听查询事件</strong></p>

<pre><code>DB::listen(function($sql, $bindings, $time)
{
    //
});
</code></pre>

<p><a name="database-transactions"></a></p>

<h2>数据库事务</h2>

<p>可以使用 <code>transaction</code> 函数在数据库事务中执行一系列操作：</p>

<pre><code>DB::transaction(function()
{
    DB::table('users')-&gt;update(array('votes' =&gt; 1));

    DB::table('posts')-&gt;delete();
});
</code></pre>

<p><a name="accessing-connections"></a></p>

<h2>获取连接</h2>

<p>当使用多个连接，您可以通过 <code>DB::connection</code> 函数获取它们：</p>

<pre><code>$users = DB::connection('foo')-&gt;select(...);
</code></pre>

<p>您也可以获取原始的，底层的 PDO 实例：</p>

<pre><code>$pdo = DB::connection()-&gt;getPdo();
</code></pre>

<p>有些时候，您可能需要重新连接给定的数据库：</p>

<pre><code>DB::reconnect('foo');
</code></pre>

<p><a name="query-logging"></a></p>

<h2>查询日志</h2>

<p>默认情况下，Laravel 在内存中保存一个包含当前请求所执行的所有查询的日志。然而，在一些情况下，比如插入很多行数据，这会导致应用程序消耗过多内存。可以使用 <code>disableQueryLog</code> 函数禁止查询日志：</p>

<pre><code>DB::connection()-&gt;disableQueryLog();
</code></pre>
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